1. Field of the Invention
The invention pertains to a longitudinal adjusting device for the seat of a motor vehicle, especially two-door motor vehicles, the back of which seat can be tilted adjustably with respect to the seat part by means of adjusting hardware, and which, after the release of an arresting device, can be flipped forward, where the seat part is attached to movable rails which can slide along guide rails permanently attached to the vehicle, and where at least one movable rail has a locking device which can be disengaged from the guide rail, to which locking device a positioning device is assigned, which makes it possible for the seat to be returned to the original longitudinal position selected for it, which positioning device comprises a positioning disk with a set of external teeth, into which the toothed segment of an arresting lever engages, which lever is supported in a fixed position with respect to the movable rail but which can be moved out of the way if needed, where, coaxial to the positioning disk, a spring-loaded winding drum is mounted, by means of which the seat part can be shifted forward by the intermediate action of a tension member permanently attached to the vehicle floor or to the guide rail, the winding drum being provided with a stop for limiting the extent to which it can be rotated in the reverse direction by a counterstop on the positioning disk.
2. Description of the Related Art
A longitudinal adjusting device of the type described above can be derived from DE 196-47,447, in which the locking device can be released in two different ways so that the seat can be shifted longitudinally. First, by lifting a release handle in the forward area under the seat, the locking device attached to the movable rail can be released via a transverse lever from the position in which it is connected to the guide rail; that is, the locking catches of the locking device are lifted out of the row of teeth on the guide rail against the force of self-restoring springs. As this occurs, the end part of the release handle carries a connecting lever along with it in the release direction; this connecting lever lifts the toothed segment of an arresting lever out of the external teeth of a positioning disk. In this case, the previously selected terminal stop position used as a guide for returning the seat to the originally selected position is lost. So that the vehicle seat can be shifted without losing the position of the terminal stop, the connecting lever is detached from the release lever by way of an unlocking lever supported on the movable rail, so that the arresting lever remains undisturbed; as a result, the locking position of the positioning disk is pre-served. Nevertheless, the unlocking lever simultaneously presses the release handle against the transverse lever, so that this lever lifts the locking catches of the locking device out of the row of teeth on the guide rail. Thus, the previously selected stop position remains preserved in the memory module, while the seat part along with the forward-tipped back can be slid forward and back again to the previously selected stop. To assist the forward sliding movement of the seat, a previously mentioned winding drum is provided, which is spring-loaded in the direction of the forward sliding movement. This drum is connected by way of a tension member either to the floor of the vehicle in the forward area of the rail arrangement or to the forward end of the guide rail. The position of the stop used as a guide for returning the seat to its originally selected longitudinal position can be adjusted when the seat is slid backwards by allowing the rotation of the winding drum, which carries another stop, to move the stop of the positioning disk along until, upon completion of the rearward sliding movement of the seat, the locking device holds the movable rail in a fixed position on the guide rail. At this point, the pivoting of the release handle back to its original position also causes the positioning disk to be held by the arresting lever, so that the position which the stop on the positioning disk reached at that time is fixed. So that the winding drum can now be allowed to make several revolutions without the need to release the positioning disk, two check rings are inserted between the stop on the positioning disk and the stop on the winding drum; these rings in turn have their own stops, which can be carried along in succession by the winding drum. Thus, while the seat is being slid backwards, the stops on the check rings move the stop on the winding drum into a stop position with respect to the stop of the positioning disk, while the stop position of the positioning disk is being maintained. To ensure that the check rings function properly, they must be installed in the correct order one behind the other; otherwise, it is impossible for the originally selected position of the seat to be restored. In addition, if it desired to allow the seat to slide a long distance, the number of check rings arranged in a row must be increased. This requires a large amount of space in the width direction, and it also increases the cost.